BIOMARCADORES DE ESTRéS COMO INDICADORES DE BIENESTAR ANIMAL EN GANADO DE CARNE: STRESS BIOMARKERS AS INDICATORS OF ANIMAL WELFARE IN CATTLE BEEF FARMING

the present review presents the physiological changes that occur in cattle during acute stress, as well as blood biomarkers used to measure their impact on animal welfare. during the pre-slaughter process, cattle are often exposed to different factors that cause physical exhaustion and physiological stress which can have adverse effects on health, animal welfare, and meat quality. the most common stressors are: fast and forced movements of the truck, centrifuged force, breakdown of the social structure due to mixing of the animals, strange environment, rough treatment of cattle during loading and unloading, weather conditions, deprivation of feed and water among others. stress has been identified as an indicator of animal welfare. stress alters the internal animal homeostasis inducing changes in the hypothalamic-pituitary-adrenocortical (hpa) axis and the sympatho-adreno-medullary system. the endocrine activation promotes the release of several hormones: catecholamines, mainly adrenaline and noradrenaline; corticotrophin-releasing hormone (crh); adrenocorticotrophin (acth) and corticosteroids, mainly cortisol. different authors have used several blood constituents to determine stress. cortisol, despite its variability and short life, is still one the most used indicators of stress. these authors have also used the packed cell volume (pcv), glucose concentration, creatine phosphokinase (ck) activity, b-hidroxybutyrate and lactate concentration as stress indicators. the determination of these biomarkers is a practical method to monitor animal welfare in cattle beef.